High-resolution Spectroscopy of the GD-1 Stellar Stream Localizes the Perturber near the Orbital Plane of Sagittarius

Bonaca, Ana and Conroy, Charlie and Hogg, David W. and Cargile, Phillip A. and Caldwell, Nelson and Naidu, Rohan P. and Price-Whelan, Adrian M. and Speagle, Joshua S. and Johnson, Benjamin D. (2020) High-resolution Spectroscopy of the GD-1 Stellar Stream Localizes the Perturber near the Orbital Plane of Sagittarius. The Astrophysical Journal, 892 (2). L37. ISSN 2041-8213

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Abstract

The 100° long thin stellar stream in the Milky Way halo, GD-1, has an ensemble of features that may be due to dynamical interactions. Using high-resolution MMT/Hectochelle spectroscopy we show that a spur of GD-1-like stars outside of the main stream are kinematically and chemically consistent with the main stream. In the spur, as in the main stream, GD-1 has a low intrinsic radial velocity dispersion, ${\sigma }_{{V}_{r}}\lesssim 1$ $\mathrm{km}\,{{\rm{s}}}^{-1}$, is metal-poor, [Fe/H] ≈ −2.3, and has little intrinsic spread in the [Fe/H] and [α/Fe] abundances, which point to a common globular cluster progenitor. At a fixed location along the stream, the median radial velocity offset between the spur and the main stream is smaller than 0.5 $\mathrm{km}\,{{\rm{s}}}^{-1}$, comparable to the measurement uncertainty. A flyby of a massive, compact object can change orbits of stars in a stellar stream and produce features like the spur observed in GD-1. In this scenario, the radial velocity of the GD-1 spur relative to the stream constrains the orbit of the perturber and its current on-sky position to ≈5000 deg2. The family of acceptable perturber orbits overlaps the stellar and dark-matter debris of the Sagittarius dwarf galaxy in present-day position and velocity. This suggests that GD-1 may have been perturbed by a globular cluster or an extremely compact dark-matter subhalo formerly associated with Sagittarius.

Item Type: Article
Subjects: AP Academic Press > Physics and Astronomy
Depositing User: Unnamed user with email support@apacademicpress.com
Date Deposited: 27 May 2023 05:07
Last Modified: 06 Jul 2024 06:51
URI: http://info.openarchivespress.com/id/eprint/1371

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